As a 1999 graduate of Jesuit High School in Beaverton, Oregon, Dunleavy led them to the 1999 4A State Boys Basketball Championship over North Salem High School , 65–38. Dunleavy attended the University School of Milwaukee for his freshman year, and Homestead High School in Mequon, Wisconsin for his sophomore year.
Dunleavy played at Duke University from 1999–2002. As a sophomore, he played on Duke’s national championship team and scored a team-high 21 points in the title game, including 3 three-pointers during a decisive 11–2 second-half Duke run. As a junior, Dunleavy was a first-team NABC All-American, averaging 17.3 points per game and 7.2 rebounds per game for the 31–4 Blue Devils.
In November 2005, the Warriors signed Dunleavy to a 5-year, $44 million contract extension.] The Warriors’ general manager Chris Mullin said, “The way Mike performed, the way he conducted himself and the way we run our organization, we both felt it was something that we wanted.”
During the 2010–2011 season, the Indiana Pacers advanced to the NBA playoffs for the first time since 2006 thanks to an end of the season win over the Washington Wizards coupled with a Charlotte Bobcats loss to the Orlando Magic. Dunleavy scored 14 points in the 136–112 victory. Dunleavy also ended his career playoff drought of 9 years and 624 games. He was the second active leader in this category behind former Warriors and Pacers teammate Troy Murphy, who also ended his drought as a part of the Boston Celtics.
Milwaukee Bucks (2011–2013)
Following the 2011 NBA lockout , Dunleavy signed a two-year, $7.5 million contract with the Milwaukee Bucks on December 10.  His best game as a Buck came on November 3, 2012 when he recorded 29 points and 12 rebounds against the Cleveland Cavaliers.
Chicago Bulls (2013–2016)
On July 10, 2013, Dunleavy signed with the Chicago Bulls on a reported two-year deal worth about $6 million.
On April 25, 2014, Dunleavy set a playoff career-high 35 points including a franchise playoff record for most three-point field goals with 8 against the Washington Wizards in game three of their 2014 NBA Playoffs first round match-up, which the Bulls won 100–97.
Cleveland Cavaliers (2016–2017)
On July 7, 2016, Dunleavy was traded, along with the rights to Vladimir Veremeenko , to the Cleveland Cavaliers in exchange for the rights to Albert Miralles. He made his debut for the Cavaliers in the team’s season opener on October 25, 2016 against the New York Knicks. In 22 minutes off the bench, he recorded four points, four rebounds, two assists and three steals in a 117–88 win. On December 23, 2016, he scored a season-high 14 points in a 119–99 win over the Brooklyn Nets.
Atlanta Hawks (2017)
On January 7, 2017, Dunleavy was traded, along with Mo Williams and a future first-round draft pick, to the Atlanta Hawks in exchange for Kyle Korver. On January 15, he scored 20 points off the bench in a 111–98 win over the Milwaukee Bucks. It was his first 20-point performance since a first-round playoff game for Chicago on April 30, 2015.
Dunleavy has two younger brothers: Baker, who played at Villanova from 2002–06 and is the current head coach at Quinnipiac;  and James, who was a walk-on for USC and is currently an NBA player agent. While growing-up, Dunleavy attended a residential sports camp in Eagle River, Wisconsin called Camp Menominee. In 2008, Camp Menominee honored Dunleavy by naming its basketball courts “The Mike Dunleavy Jr. Courts”.